Flexible skirt piston



L. R. DAVIS FLEXIBLE SKIRT PISTON Filed July 27, 19.25

June 29 192 1,590,616

-: xix

5 Lew/s i 0.410s

W 35 M a Patented June 29, 1 926.

UNITED STATES LEWIS R. ZDA VIS, OF SAN rmcrsoo, camnonnm FLEXIBLE sxmrPISTON.

Application filed July 27, 1925. Serial No. 46,445.

This invention relates to pistons of the split skirt type especiallythose adaptable forinternal explosive engines, and the objects of theinvention are to provide a split 5 skirt piston construction which iseasily produced byordinary molding or die casting processes which willeffect a perfect. fit to the cylinder to compensate for considerablewear thereof, and which will greatly reduce" 1 the oil pumping tendencycommon to such pistons. Other advantages of my construction will appearin the following description. The drawings accompanying thisspecification show the preferred embodiment of the invention, it beingunderstood that such minor changes as fall withinthe spirit thereof areintended to be covered in the claims hereto appended.

Figure 1 of the drawing is an external view ofmy piston. I

Figure 2 is a vertical section through the center thereof.

Figure 3 is a transverse section of the piston as taken along the line3-3 of Figure 2.

In 7 further detail mypiston comprises a head 1 cast with a cylindricalwall 2, and a pair of opposed bosses 3 adaptedv to take the wrist pin 4of a connecting-rod 5.

The bosses 3 are rigidly braced to the wall and head by an integrallycast rib 6 extending across the under side of the head 1. Thecylindrical Wall 2 is of reduced I diameter from its lower edge to apoint 5 A above the bosses, and surrounding this reduced'portion is anouter flexible wall or split skirt 7.

1 This skirt p 7 is spaced from the reduced wall by an annular space 8preferably l0 slightlylarger at the bottom as indicated in Figure'2, sothat in die casting the core die may be easily pulled out. The skirt iscast integrally with the body of the iston, being connected thereto by alug 9 ad jacent 5 which the skirt is slotted fromend to end afterfinishing as shown at 10.

The lug 9 and slot 10 may be vertical but I prefer to run them on aspiral, as indicated in Figure 1, so that theskirt in expanding, tocompensate for cylinder wear,

will better preserve its rotundity.

The lug 9 may be of any desired proportions and located directlyat thepoint of slotting or spaced therefrom, or. if desired two lugs may beused andalso' two slots,

this all depending on the amount of flexibility desired in theparticular piston.

In casting the piston and skirt the space 8 may terminate as indicatedat 8' and the skirt is extended as indicated at 7' to connectintegrallywith the piston body, so that it forms a firm unit forturning, grinding or boring for the wrist pin, etc., after which two oilring grooves 11 are turnedin the upper end of the piston and finally athird groove 12 which penetrates the cored space '8 and separates theupper end of the skirt from the body of the piston.

The skirt is bored at 15 to clear the pin 4 so that the skirt will befreelto expand against the cylinder walls, and just below the bosses 3 asplit expanding or bull ring 13 is seated in a very shallow groove 14turned in the inner surface of .the skirt.

In using the iston the usual split rings are inserted in t e grooves 11and 12 and a ring in the latter, it will be noted, will be supportedbetween an upper wall formed on the body of the piston and thesubstantially free upper end of the skirt. This construction provides aflexible skirt supporting the lower ring and with a free annular passage8 extending from the skirt and body ofthe piston o en'at almost theentire circum: ference of t e piston to the lower oil ring roove. Thus,the annular passageway 8 unctions to completely drain any surplus oilfrom the lower groove back into the crank case, and the reduced'diameterof the 1 piston body acts as a bafile wall to prevent oil being throwninto the passageway, and the bull ring positioned to almost, cover thelower end of the passageway prevents any oil being thrown u wardly, intothe passage, thus insuring t atihe oil will not rise in in'uriousamountabove the lower ring, and t e skirt itself beingsplit from end toend and spaced from the body of the piston acts like a very long ringalmost independ ent of the body, thus effectually compensating for allwear of the walls.

1. A' piston chmprising a' head portio having a reduced lower end ofannula cross-section throughout, the said reduced lower end, being boredat opposite points i above its lower edge to'provide wrist pin bosses, asplit skirt surrounding the. said reduced lower end; portion andextending above the wrist pin bosses and a rib connectedto the reducedlower end portion and to the skirt for supporting the latter in spacedrelation to the head and to the said lower end portion.

2. A piston comprising a head, a split skirt located belowthe head andaced therefrom, the said head having are nced lower end portion ofannular cross-section extending into theupper end of the skirt anddownwardly therethrough and spaced therefrom and operating to provide abattlefor intercepting lubricant entering upwardly through the lower endof the skirt and directing the lubricant inwardly and away from theadjacent intervening space, said reduced lower end portion havingoppositely disposed wrist in bosses located below the upper end 0 theskirt, and a rib connected to the said lower end portion of the head andto the skirt and for sup orting the latter in s aced relation to the eadand to the said re uced end portion thereof.

3. A piston comprising a head, a split skirt located below the head andspaced therefrom, the said head having a reduced lower end portion ofannular cross-section extending into the upper end of the skirt anddownwardly therethrough and spaced therefrom and operating to provide abattle 'for intercepting lubricant entering upwardl through the lowerend of theskirt and lrecting1 the lubricant inwardly and away from t eadjacent intervening space, said reduced lower end portion havingoppositely disposedwrist pin bosses locatedbelow the upper end of theskirt, a rib connected to the said lower end portion of the head and tothe skirt and for supporting the latter in spaced relation to thehead-and to surrounding the lower part of the body portion and spacedtherefrom, said sleeve being split from end to end along a spiral lineand integrally connected to the lower part of the body portion by a castspiral lug lying adjacent one edge of the s lit.

' LEWIS R. AVIS.

